Catalytic reduction of organic chloro-nitro compounds



Patented May 13, 1947 UNRTE STATES PATENT ori ice CATALYTIC REDUCTION OFORGANIC CHLORO-NITRO COMPOUNDS James A. RobertsomElsmere, DeL, assignorto E. I. du Pont de Nemours & Company, Wilmington, Del., a corporationof Delaware No Drawing. Application August 25, 1945,

Serial No. 612,707

may also be made by the reduction of aliphatic nitrocompounds withstannous chloride in bydrochloridic acid. N-substitutedalkylhydroxylamines are likewise produced by various chemical methodsfor the reduction of nitrocompounds. The prior art methods, however, aregenerally not adapted to commercial operations, or possess disadvantagesthat make them undesirable because of low yields, complicatedprocedures, or other reasons.

An object of the present invention is a new andimproved method for theproduction of oximes and substituted hydroxylamines. A further object isa method for the reduction of chloro-nitrocompounds and the preparationof ,oximes and hydroxylamines therefrom. A still further object is aneflicient catalytic hydrogenation process for such production.Additional objects will be disclosed as the invention is described morefully hereinafter. p

I have found that the foregoing objects are accomplished when hydrogenis reacted with an organic nitrocompound having a halogen atom and anitro group attached to the same carbon atom and the reaction is carriedout in the substantial absence of an aqueous medium and in the presenceof a. platinum metal hydrogenation catalyst. Desirably a volatileorganic solvent is present in the reaction vessel. While the inventionhas been broadly stated to involve compounds having a halogen group onthe same carbon atom with the nitro group, chloro-nitro compounds willbe the ones ordinarily treated because of their greater attractivenesseconomically and the favorable results obtained.

The following will serve as specific examples to illustrate theprocedure of the invention. It i will be understood that these are notlimiting in any way. The amounts used are parts by weight, unlessotherwise stated.

Example 1 i I 2 n.

2 l-nitrocyclohexane, 100 parts by volume of methanol and 1.63 parts of10% palladium-on-charcoal was introduced into a Pyrex pressure bottleand subjected to a hydrogen pressure of 40 lb. at ,7

room temperature. Agitation was started and 0.4 part of hydrogen wasabsorbed during 20 minutes. The contents of this bottle were discharged,the catalyst removed by filtration, and the filtrate neutralized with anaqueous solution of 6.9 parts of potassium carbonate. The filtrate wasevaporated to dryness under reduced pressure. The

residue was dissolved in an aqueous solution of sodium hydroxide andprecipitated by acidification with hydrochloric acid. The white solid,cyclohexanone oxime, was collected on a filter and dried. It had amelting point of 895 C. and the yield was 8.5 parts, of theoretical.

'- In another preparation of cyclohexanone oxime, by a similar procedurebut starting with separately prepared 1-chloro-1-nitrocyclohexane, ayield of was obtained.

. Example 2 Eight parts of l-chloro l-nitrocyclohexane, 50 parts byvolume of ethanol and 0.16 part of platinum oxide were mixed in a Pyrexressure bottle and subjected to 40 lb. hydrogen pressure at roomtemperature. During /z hour, 03 part of hydrogen was absorbed, and thecontents of the bottle were then discharged. The catalyst was removed byfiltration and the filtrate evaporated to dryness under reducedpressure. The

residual white solid, identifiedas cyclohexylhydroxylamine hydrochloridewith a melting point of 142 C., weighed 6.5 parts, which was 80% of thetheoretical yield.

Example 3 hydrogen was absorbed during /2 hour, after which the contentswere discharged. The catalyst was removed by filtration and the filtrateneutralized with an aqueous solution of 6.9 parts of potassiumcarbonate. After drying under reduced pressure, the residue consisted of3 parts of acetone oxime, with a melting point of 56-58 C., the yieldamounting to 36% of the theoretical.

The foregoing examples have cited some speciflc chloronitrocompoundsthat have been used in the preparation of oximes and substitutedhydroxylamines in accordance with the invention. It will be understood,however, that many other such compounds are likewise suitable, arequirement being that the chlorine or other halogen atom shall beattached to the same carbon atom as is the nitro group. The followingadditional materials may be employed in similar manner: 2 chloroZPnitrobutane, 2-methyl-3-chloro-3- nitrobutane, 2-bromo-2-nitrobutane,l-phenyl- 2 chloro-2- itropropane, l-phenyl-l-chloro-lnitroethane,9-chloro-9-nitrofluorene, and many others. I

The use of a solventlathe reaction vessel is like.

temperatures up in the range -50 be carried out at atmospheric pressure,superatmospheric ressure will ordinarily be employed, generally inexcess of lb. per square inch, as a practical rate of reaction isobtained under such pressure conditions. The upper limit is determinedby the structural limitations or the equip ment used, and may be ashighas 1000-5000 lb. per square inch.

As has been stated, in the presence tion catalyst. This is metals andincludes platinum, palladium, metals and their oxides and salts beingapplicable. In many casesit will be desirable to have the catalystsupported on a carrier of suitable material. The catalyst used will belargely dependent on the reduction product desired. When the preparationof oximes is intended, I desirably iridium, osmium,

employ finely divided palladium, which may ad,- v

vantageously be supported on charcoal, alumina, silica gel, or othermaterial. If on the other hand, N-substituted hydroxylamines are desiredas products, finely divided platinum, in the form,

The process of the invention is operable at to 100 C.. Preferably Ioperate C. While the reaction may amines, 1'I'hese products are usefulintermediates in the "synthesis of polymeric organic compounds.

. pharmaceuticals, and insecticides, etc. While the the inventio Iintend .iollowing claims.

suitable are methanol, ethanol, propanol, dioxan, cyclohexane, and the 1tion is carried out understood that procedures, compositions and poundconsisting solely-of it will be many variations in details of the likemay be introduced without departure from the scope of to be limited onlyby the process has been disclosed adequately;

Iclaimfi catalytic reduction of .nitrocompounds' which comprisesreacting hyc nitrocompound having a nitro group attached to the and 2.atom, the remainder oi the comcarbon-a'nd hydrogen, the reaction in the"substantial absnce'of an aqueous medium in the presence or a a platinumgroup metal hydrogenation catalyst.

halogen atom samejcarbcn and effecting 2. The' process of claim 1 inwhich the reacat superatmospheric pressure. for the catalyticreductlono! to produce a hydroxylamine 3. Thei' process nitrocoinpounds whichcomprises reacting hydrogenzwith anorthe process is carried out. of aplatinum metal hydrogenaawell-understood class of rhodium, andruthenium, both the iree of the free metal, its oxides or salts, ispreferably-j used. An amount of catalyst is chosen that will bring aboutreaction at the desired rate, and De-2 tween 0.01 and 10.0% by weight ofthe chloro-ff nitro compound may desired at a rapid rate and catalysteconomy is important,

be used. When reduction is at relatively low temperature, an amount of 1to 10% is desirable. Iii,

advantageously be extended Number ganic nitrocompound 'tiie and inthe-presence of a platinumcatalyst.

I having a'halogen'atom and a, nitrogjroup attached to the same carbonatom, the remainder of the compound consisting solely or carbon andhydrogen, and eiiectingthe reaction substantial absence of an aqueousmedium 4. The process for the catalytic reduction of nitroconipounds toproduce an-oxime which comprisesfireacting hydrogen with? an organicnitrocompound having a halogen atom and 9. nitro group attached to thesame carbon atom,:the remainder of the compound consisting solely ofcarbon and hydrogen, and effecting the reaction in the substantialabsence of an aqueous medium in :the presence of a palladium catalyst.

5. The process of producing cyclohexylhydroxylamin'e whichcomprisesre'acting 1-chlorol-nitrocyclohexane with hydrogen in the pres-";ence or a} platinum catalyst.

' fifi'lhe process of producing cyclohexanone crime which comprisesreacting l-chloro-l-nitrocyclohe'xan'e with hydrogenin the presence of apalladium catalyst.

' JAMES A. ROBERTSON.

' REFERENCES CITED The following references are of record in the file ofthis patent:

UNITED STATES PATENTS Name Date 1 1,907,820 Jaeger May 9, 1933Certificate of Correction Patent No.n2,420,382. May 13, 1947. JAMES A.ROBERTSON It is hereby certified that error appears in the printedspecification of the above numbered patent requiring correction asfollows: Column 1, lines 15 and 16, for hydrochloridic readhydrochloric; and that the said Letters Patent should be read with thiscorrection therein that the same. may conform to-the record of the casein the Patent Office.

Signed and sealed this 8th day of July, A. D. 1947.

[SEAL] LESLIE FRAZER,

First Assistant Commissioner of Patents.

